1. Field of the Invention
The present invention relates to an inkjet recording apparatus. In particular, the present invention relates to a line head type inkjet recording apparatus.
2. Description of Related Art
Generally, among inkjet recording apparatuses, there are for example those of the serial head type in which a recording head is moved on a recording medium in a reciprocating manner so that the recording medium is conveyed in a direction orthogonal to a scanning direction of the recording head to form an image or those of the line head type in which a recording head fixed to have a nozzle row extending along the width of a recording medium so that the recording medium is conveyed in a direction perpendicular to the direction of the nozzle row to form an image.
In the line head type inkjet recording apparatus 50, the position or direction of the nozzles of the recording head 53 is dislocated to cause, as shown in FIG. 46 to FIG. 48, the displacement of ink jetting positions. This causes a case in which, even when the respective nozzles jet the same amount of ink, the stripe uneven recording 51 may be frequently generated in a direction along which the recording medium 52 is conveyed, causing a significant deterioration of image quality.
Thus, in order to prevent the deterioration of image quality as described above, various methods have been suggested. One method intends, for example, to use a so-called interleave to disperse the dislocations of ink jetting positions so that stripe uneven recording is reduced. The term “interleave” herein means a method in which a recording of a plurality of neighboring pixels is completed by a plurality of scanning operations.
Specifically, in a method for an image recording apparatus having a line head type recording head and a drum-like recording medium retention section, the recording medium retention section is rotated together with a recording medium so that a plurality of recordings are performed in an image recording of one scanning to record pixels such that every “n” pixel(s) (“n” is an integer of one or more) is/are recorded in at least one of a direction in which nozzles are arranged or a direction in which the medium is conveyed, thereby completing the image. As a result, dislocations of ink jetting positions can be dispersed, thereby reducing the deterioration of the image quality due to uneven recording or the like (see JP-Tokukai-2002-11865A).
When an image recording is completed by a plurality of scannings in an image recording apparatus having a line head-type recording head and a flat plate-like recording medium retention section, it is necessary to convey, in a reciprocating manner repeatedly, a recording medium at the lower part of the recording head while switching the conveyance directions. Thus, there is one method in which an image recording is completed by repeating a step for moving, when the conveyance direction of a recording medium is switched during the conveyance of the medium in a reciprocating manner, the position of the recording head in the nozzle arrangement direction. With this method, even an image recording apparatus having a flat plate-like recording medium retention section can perform a image recording by a plurality of scannings with the resolution equal to or higher than a nozzle interval of the recording head (see JP-Tokukai-2002-36530A).
However, when the line head type inkjet recording apparatus having a flat-surface-like recording medium retention section performs an image recording by the above interleave, an image recording is completed by a plurality of scannings in which the front end or rear end of a recording medium is conveyed at the lower part of the recording head to subsequently invert the conveyance direction of the recording medium to convey the recording medium in a reciprocating manner. This causes, as shown in FIG. 49, the conveyance amount L in the conveyance direction of the recording medium in one scanning to be larger than the sum of the length Lm of the recording medium and the length Lh of a region including the plurality of recording heads 53. This has caused a problem in conventional inkjet recording printers in that an increased time is required for the image recording when the plurality of recording heads 53 are used because the conveyance amount L for one scanning is increased and an image recording to another recording medium cannot be started until recording to the current recording medium is completed by performing a predetermined number of scannings.
When a recording is performed by the plurality of recording heads 53, the time from a recording by the first recording head 53 to a recording by the second recording head 53 is short. Thus, ink jetted from the second recording head 53 is performed within a time in which ink jetted from the first recording head 53 is not sufficiently absorbed by the recording medium 52, causing a problem in which a plurality of inks jetted from different recording heads have a bleeding, causing the deterioration of the image quality.